Hitherto, there are electronic equipments using a vibration generating device for transmitting vibration to user. As an example, there can be mentioned portable or mobile telephones. Such mobile telephones have such a configuration to generate vibration at the time of the so-called manner mode to thereby have ability to notice message arrival (calling) to user. In such mobile telephones, a vibration generating device as a vibration actuator adapted for generating vibration is included therewithin.
As a vibration generating device used in mobile telephone, there is a vibration generating device constituted as shown in FIG. 1. In the vibration generating device 1 shown in FIG. 1, a weight 4 is fixed to an output shaft 3 of a motor 2 with brush in the eccentric state with respect to the output shaft 3.
The vibration generating device 1 takes out, as vibration component, rotation unbalance energy generated as the result of the fact that the output shaft 3 is rotated by drive of the motor 2 so that the weight 4 is eccentrically rotated. In such vibration generating device 1, there are problems as described below.
When the motor 2 with brush is used as a drive source, since unsatisfactory phenomenon in rotation due to the so-called slit short, etc. cannot be zero, there is the problem that there lacks in reliability of vibration generating operation.
The motor body can be reduced to, e.g., about 3.5 mm in diameter, but there is the problem that it is required to increase the number of rotations for the purpose of obtaining vibration energy of a desired magnitude so that power consumption is excessively elevated followed thereby. In portable or mobile electronic equipments using battery as a power source such as mobile telephone, elevation of power consumption is not preferable from a viewpoint of battery life, etc.
Moreover, when attempt is made to reduce the diameter of the motor body to dispose the weight at the inside of the motor diameter, it fails to set, to a large value, quantity of eccentricity of weight for generating rotation unbalance energy. As a result, vibration component would be reduced.
In order to set quantity of eccentricity of the weight to a large value, it is required to fit rubber ring, etc. with respect to the output shaft to attach the weight to the rubber ring, etc. to ensure quantity of eccentricity of the weight, or to amplify the vibration component so that realization of thin structure and miniaturization of the vibration generating device 1 resultantly becomes difficult. In addition, there is also the problem that since the number of parts is increased, it is difficult to realize reduction in cost, or increase in the number of parts lowers the reliability of the vibration generating operation.
In view of the above, the applicant has proposed, in the Specification and the Drawings of the Japanese Patent Application No. 2002-186555, a vibration generating device in which the weight is provided at the eccentric position of the rotor provided at the plane opposite type motor where the rotor magnet and the stator coil are disposed in a manner flatly opposite to each other.
In the vibration generating device, since the rotor and the stator are opposed in a plane manner, realization of thin structure and miniaturization can be made. Moreover, since the diameter of the rotor can be set to large value, quantity of eccentricity of the weight can be taken as a large value. Large rotation unbalance energy can be obtained as compared to mass of the weight. Thus, large vibration can be obtained by small power consumption. Since this motor is brushless motor, there is no possibility that unsatisfactory phenomenon in rotation by the so-called slit shot may take place. Thus, device having high reliability is provided.
Meanwhile, the vibration generating device proposed in the Specification and the Drawings of the above-mentioned application is caused to be of the configuration in which assembly is made such that respective members constituting the rotor, i.e., the shaft, the rotor yoke, the rotor magnet, the ring and the weight are all formed as individual parts thereafter to fix the ring to the shaft to fix the rotor yoke to the ring to fix the rotor magnet and the weight to the rotor yoke. For this reason, not only the number of assembling steps is increased, and the cause such that manufacturing cost is elevated is constituted, but also it is necessary to form mutual coupling portions for assembling at respective members constituting the rotor so that there are limits in miniaturization of the rotor itself and miniaturization of dimensions in the axial direction of the shaft, i.e., realization of thin structure.
In addition, it is necessary to provide bearing unit for rotatably supporting the shaft of the rotor at the stator so that realization of thin structure is limited to such a degree that the thickness of the bearing device, i.e., the size in the axial direction is required.